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Improving the stability of sensitive catalytic systems is an emerging research topic in the catalysis field. However, the current design of heterogeneous catalysts mainly improves their catalytic performance. This paper presents a single-atom catalyst (SAC) strategy to improve the cobalt-catalysed fluorination of acyl chlorides. A stable Co-F intermediate can be formed through the oxidative fluorination of Co

Single-atom site (SAS) catalysts have attracted considerable attention due to their excellent performance. However, most of the current research models of SAS catalysts are based on inorganic catalysts, where “metal and coordination atom interaction” cannot simulate the fine-tuning effect of organic ligands on metal catalytic centers in homogeneous catalysts. Therefore, certain chemical transformations in homogeneous catalysis cannot be perfectly replicated. Here, we used porous organic ligand polymers as the carrier, which effectively changes the charge regulation of nanoparticles and monoatomic metal catalysts. Drawing lessons from traditional homogeneous metal/ligand catalysis, we introduced various functional groups into the ligand polymers to adjust the electronic properties, and successfully realized the hydrosilylation of internal alkynes with high catalytic performance. The selectivity and catalytic efficiency under the Pd@POL-1 catalyst system were improved compared with previous studies. The internal alkynes with various structures can complete this reaction, and the ratio of E/Z can reach up to 100:1.

This study proposes two different methods of photocatalytic-controlled and visible light-induced selective oxidation of pyridiniums with air as the terminal oxidant. The key to these transformations is to choose the appropriate light source and photocatalyst. Pyridiniums are successfully converted into pyrroles through oxygen-mediated cycloaddition, proton-coupled electron transfer (PCET), pyridine ring opening, and recyclization. The other route is that pyridiniums selectively form 4-carbonyl pyridines through free radical rearrangement/aerobic oxidation under the catalysis of cobalt (II).

The study reported an electrochemically mediated method for the preparation of 2,1-benzoxazoles from o-nitrophenylacetylenes. Different from the traditional electrochemical reduction of nitro to ni...

Organic reactions using metal–organic frameworks (MOFs) as catalysts are promising with regard to their environmentally friendly features and potential catalyst recyclability. A robust Co(II)-MOF {[Co2(L-mac)(4,4-bpt)(H2O)]·3.5H2O}n (1) and its enantiomer {[Co2(D-mac)(4,4-bpt)(H2O)]·3.5H2O}n (2) (L/D-mac = basic forms of L/D-malic acid, 4,4-Hbpt = 3,5-di(pyridin-4-yl)-4H-1,2,4-triazole) have been gram-scale prepared under solvothermal conditions. Structural analysis reveals that mac manages Co(II) ions to form 1-D chains, which are further extended via 4,4-bpt connectors into a noninterpenetrating 3D framework architecture. It was found that 1 can be as a heterogeneous catalyst for multiple organic reactions, such as azide-alkyne cycloaddition and Friedel–Crafts reactions with good isolated yields and good recycle runs (at least five times without substantial degradation). Additionally, 1 can promote hydrosilylation of alkynes under harsh conditions with moderate yield.

Summary Single-atom-site (SAS) catalyst, as a highly reactive heterogeneous catalytic system, is one of the effective tools for complex organic synthesis. However, excessive attention on the catalysis and regulation of metal atoms has led to the neglect of the role of supports and ligands. Here, we employed a P-doped porous organic polymer as a support, as well as a ligand in the developed Pd SAS catalysts. The enrichment of the substrates by the pores, ligand action of the support, and high chemoselectivity and anti-agglomeration of SAS catalysts were the most striking features of this SAS catalyst. A highly selective distannylation of terminal alkynes with a new mechanism was achieved by using the multiple properties of SAS catalyst. This catalytic system offers an effective strategy to utilize the enrichment of the substrate by the pores to regulate the reaction mechanism, which opens a new frontier to use pores, ligands, and SASs for synergistic controlling reaction paths.

The study reported an electrochemically mediated method for the preparation of 2,1-benzoxazoles from

Selective C1–H/C4–H carbonylation of N-methylene iminium salts, catalyzed by visible-light photoredox and oxygen in the air, has been reported. A ruthenium complex acts as a chemical switch to conduct two different reaction pathways and to afford two different kinds of products. In the absence of the ruthenium complex, the Csp2–H bonds adjacent to the nitrogen atoms are oxidized to α-lactams by the N-methyleneiminium substrates themselves as photosensitizers. In the presence of the ruthenium complex, the oxidation reaction site of quinoliniums is switched to the C4 region, resulting in the formation of 4-quinolones. The use of two transformations directly introduces oxygen into the nitrogen heterocyclic skeletons under an air atmosphere.

A convenient and efficient palladium-catalyzed approach has been developed for the synthesis of 5-amino-1,2,4-oxadiazoles from amidoximes and isocyanides. Various 5-amino-1,2,4-oxadiazoles were obtained in moderate to high yields under mild conditions. The key to the success of this strategy involves new C-N bond and C-O bond formation via palladium-catalyzed isocyanide insertion.

Building new biological molecules is challenging. Herein, imidazo[1,2-c]thiazoles were synthesized as a new class of heterobicyclic analogs through Pd-catalyzed cascade bicyclization from isonitriles with thioamides. The bicyclic scaffolds were constructed by inserting three molecules of isonitrile into two molecules of thioamide and then cyclizing them in a one-pot procedure. In vitro antitumor studies of these new compounds were conducted by using the MTT assay, and compound 3c showed excellent inhibitory effects against HepG2 at 7.06 ± 0.68 μM.

A porous organic polymer (POL-Xantphos) was synthesized and employed as a heterogeneous ligand for selective hydrosilylation of alkynes. It exhibits high selectivity and catalytic efficiency toward a broad range of alkynes. Owing to the confinement effect of the micropore structure, POL-Xantphos was far superior to the monomeric Xantphos ligands in controlling the selectivity. By performing hydrosilylation in a flow reactor system, separation and regeneration of the Ni/POL-Xantphos catalyst are easily achieved without any loss in selectivity or activity.

A Co(acac)2 /POL-Xantphos@10PPh3 -catalyzed hydrosilylation of unsymmetrical internal alkynes with Ph2 SiH2 has been developed for the synthesis of highly selective syn-α-vinylsilane products. Furthermore, terminal alkynes were also used and gave the products with excellent regioselectivity and a wide functional group tolerance. Because this porous organic polymer combines the selectivity and activity merits of Xantphos with the stability advantage derived from the high concentration of PPh3 , the Co(acac)2 /POL-Xantphos@10PPh3 can be recycled multiple times without loss of activity and selectivity. This heterogeneous catalyst is expected to find promising applications in industrial synthesis.

A new method for the synthesis of multisubstituted guanidines through tandem intermolecular insertion of isonitriles with un­activated amides has been developed. In this study, isonitriles could be used not only as reaction materials but also as the source of amines.

A simple and efficient Cu-catalyzed decarboxylative/click reaction for the preparation of 1,4-disubstituted 5-arylselanyl-1,2,3-triazoles from propiolic acids, diselenides, and azides has been developed. The mechanistic study revealed that the intermolecular AAC reaction of an alkynyl selenium intermediate occurred. The resulting multisubstituted 5-seleno-1,2,3-triazoles were tested for in vitro anticancer activity by MTT assay, and compounds 4f, 4h, and 4p showed potent cancer cell-growth inhibition activities.

A new type of phosphorus-doped porous organic polymer (POP) has been readily synthesized through a Heck reaction, which could be used not only as a support but also a ligand for palladium nanoparticles. The dual-functional material supported palladium nanocatalyst was used for the efficient and chemoselective hydrogenation of varieties of nitroarenes and α,β-unsaturated compounds, as well as for the synthesis of indoles from 2-nitrophenylacetonitrile under 1 atm hydrogen in green solvents at room temperature. No obvious aggregation and loss of catalytic activity of the new nanocatalyst were observed after 10 runs in the reaction.

C-centered radical cyclization under electrochemical conditions is a feasible strategy for constructing cyclic structures. Reported herein is the electrochemical synthesis of highly functionalized 1-naphthols using alkynes and 1,3-dicarbonyl compounds by (4 + 2) annulation of C-centered radical. Electrolysis was conducted with Cp2Fe as redox catalyst, thereby eliminating the use of oxidants and transition-metal catalysts. The synthesized 1-naphthol compounds showed good antitumor activity in vitro, and further studies indicated that compound 3bl induced tumor cell apoptosis.

Heterogeneous, metal, single-site catalysts often exhibit higher catalytic performance than other catalysts because of their maximized atom efficiency of 100 %. Reported herein is a precoordination/solvothermal polymerization strategy to fabricate a stable mononuclear Pd-metalized porous organic polymer catalyst (Pd@POP). Pd@POP was easy to use in regioselective organic reactions because the internal structure of this Pd@POP can be easily modified. The catalyst was used to solve the intractable regioselectivity problems of Heck reactions. Pd@POP-9 can efficiently activate the ends of olefins, thereby leading to high selectivity for substitution at the external position. To understand the reason underlying the high selectivity and activity of the catalyst, the systemic characterization of Pd@POP-9 and density-functional theory calculations were conducted. This Heck reaction is the first to be catalyzed by a recyclable mononuclear metal catalyst with unprecedented catalytic activity and regioselectivity.

A novel palladium nanoparticle (NP)-metalated porous organic ligand (Pd NPs/POL-xantphos) has been prepared for the chemoselective decarbonylation of aldehydes. This heterogenous catalyst not only has excellent catalytic activity and chemoselectivity, but also holds high activity after 10 runs of reuse. The effective usage of this method is demonstrated through the synthesis of biofuels such as furfuryl alcohol (FFA) via the highly chemoselective decarbonylation of biomass-derived 5-hydroxy-methylfurfural (HMF) with a TON up to 1540. More importantly, 9-fluorenone could be obtained in one step through the decarbonylation of 2-bromobenzaldehyde by using this heterogeneous catalyst.

Two types of thiazole derivatives are synthesized through a multistep cascade sequence with Pd-metalated phosphorus-doped porous organic polymers (POPs) as heterogeneous catalysts. The POPs could be used as both ligands and catalyst supports. No obvious aggregation and loss of any catalytic activity of the catalysts were observed after 10 runs of the reaction. More importantly, imidazo[4,5- d]thiazoles, which are a new class of thiazole derivatives, could be obtained through K2CO3-promoted intramolecular cyclization of the synthesized polysubstituted thiazoles. Furthermore, the in vitro anticancer activity of these new compounds were tested with MTT assay, and compound 4b exhibited good antitumor activity toward T-24 and A549 cells with IC50 values of 10.3 ± 0.8 and 11.8 ± 0.5 μM, respectively. In addition, the action mechanism of 4b on tumor cells was determined.

A regioselective efficient synthetic approach to N-imino-γ-carbolinium ylides via AgOTf-catalyzed iminoannulation has been developed. This transformation proceeds via a silver(i) triflate-catalyzed consecutive Friedel-Crafts reaction/N-C bond formation sequence between the readily available indole derivatives and propargylic alcohols.

A new method for the stereoselective synthesis of highly substituted (1E,3E)-2-sulfonyl-1,3-dienes from N-propargylic sulfonohydrazone derivatives has been developed via copper(I)-catalyzed [3,3] rearrangement and highly regioselective migration of the sulfonyl group.

A highly efficient AgOTf catalyzed [3,3] sigmatropic rearrangement/1,3-H shift/6π aza-electrocyclization cascade reaction of N-propargylic hydrazones has been developed. This method provides a new mild synthetic route to various polysubstituted 1,6-dihydropyridazines including the 3-CF3-substituted ones with high selectivity.

A highly efficient AgOTf catalyzed [3,3] sigmatropic rearrangement/1,3-H shift/6π aza-electrocyclization cascade reaction of N-propargylic hydrazones has been developed. This method provides a new mild synthetic route to various polysubstituted 1,6-dihydropyridazines including the 3-CF3-substituted ones with high selectivity.

α-Amino ketones are synthesized starting from aldehydes, hydrazines, and α-haloketones via a novel, efficient, Cs2CO3-promoted cascade condensation/nucleophilic substitution/ N-N bond cleavage sequence in one-pot.

An efficient gold-catalyzed cyclization/arylidene group transfer cascade reaction of N-propioloyl hydrazones has been developed. This method provides a novel approach for the synthesis of various functionalized 4-arylidenepyrazolones.

The method is applied to the one-pot preparation of pyrazolo[1,5-c]quinazoline (XIII) by in situ oxidation of the corresponding 5,6-dihydropyrazolo[1,5-c]quinazoline product.

The method tolerates various functional groups, thus offering a convenient access to highly functionalized pyrazoles including medicinally relevant 3-trifluoromethyl substituted derivatives [cf.

The transformation proceeds via a Friedel—Crafts-type substitution of a propargylic cationic species, generated from (II) and (V), with indoles followed by intramolecular N—C bond formation.

An efficient method for the preparation of 5,6-dihydropyrazolo[1,5-c]quinazolines via gold(I)-catalyzed chemoselective bicyclization of N-propargylic sulfonylhydrazones has been developed. This process relies on the chemoselective cyclization of the hydrazone nitrogen instead of the usually favored aniline nitrogen onto the alkyne. The synthetic utility of the current strategy is demonstrated through the synthesis of a potential Eg5/Kinesin spindle protein inhibitor.

An efficient Cs2CO3-promoted synthesis of α-amino ketones using hydrazines, aldehydes, and α-haloketones as starting materials through a cascade condensation/nucleophilic substitution/N-N bond cleavage route is developed. The carbonyl group plays a key role in this novel N-N bond cleavage process.

A new method for the synthesis of highly substituted (1E,3E)-2-sulfonyl-1,3-dienes (II) from hydrazones (I) is developed via Cu(I)-catalyzed [3,3]-rearrangement and highly regioselective migration of the sulfonyl group.